In recent years, there has been developed a fuel cell vehicle rapidly, and as one method to extend a mileage, there has been developed a high-pressure hydrogen tank that supplies hydrogen to the fuel cell. Incidentally, the hydrogen tank has a columnar outer shape and one end thereof is formed with a cylindrical mouth ring (inserted member). Then, by inserting and screwing a valve body (insertion member) into the mouth ring, a filling chamber to seal high-pressure hydrogen is formed.
Further, an annular accommodation region is provided between the valve body and the mouth ring, and an O-ring made of rubber is mounted on the accommodation region in order to prevent a leakage of hydrogen. Furthermore, backup rings may be provided adjacent to the O-ring in order to prevent the O-ring from being damaged by biting into a gap between the valve body and the mouth ring.
Patent Document 1 (Japanese Patent Application Publication No. 2002-161983) describes a sealing device including a seal ring (O-ring) and two backup rings sandwiching the seal ring in an annular mounting groove provided on one member out of a housing (inserted member) and a shaft (insertion member) assembled coaxially with each other. In addition, the two backup rings are mounted so that inner peripheral surfaces thereof abut against tapered groove portions provided on both ends of the mounting groove.